NetEq: Use TickTimer in DelayManager

This change replaces packet_iat_count_ms_ and max_timer_ms_, two
time-counting member variables in DelayManager, with Stopwatch objects
obtained from a TickTimer.

BUG=webrtc:5608

Review-Url: https://codereview.webrtc.org/1929863002
Cr-Original-Commit-Position: refs/heads/master@{#12554}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 8f8c96d1924c96f3a5c149ca31883d296ddceca7
8 files changed